Booting the TS-7300 boards

1
Booting the TS-7300 boards

• VHDL and C

2
Overview

• After looking at the general approach to booting
  machines (generally PCs) we will now look at the
  TS-7300 board
• Firstly some general observations on booting
  embedded boards
• They quite often dont have hard drives
• They are frequently low power
• Need to drop into background low power mode
• They use un-attended boot mode.
• They will use specialised/stripped down kernels.

3
TS board gotchas

• The TS-7300 differs from more commonly found
  boards in a number of ways
• It doesnt have on-board flash, so there is no
  real BIOS/BSP to speak of
• It boots of an SD (Secure Digital) disc, so it
  use proprietory code

4
TS-7300 boot sequence

• On power on the ARM EP9302 CPU search for an on
  board boot device
• It can find them in a number of places
• FLASH memory
• UART (ay 9600 baud!)?
• SPI interface
• It looks for a boot image to run either the OS or
  a BIOS/BSP

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TS-7300 boot sequence

• On the TS-7300 board the SPI interface is used to
  talk with a 2k serial EEPROM
• The EEPROM has the string CRUS meaning that
  this is a bit of boot code
• The TS board downloads the 2k of code in the
  EEPROM into on-chip SRAM and executes it.

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TS-7300 boot sequence

• The EEPROM code does some self testing, sets up
  SDRAM, bus timing, and Ethernet MAC addresses
• There is an (unused on our system) 36 byte
  security block at the end of the EEPROM that
  allows many security options.
• Passwording
• Locking to a specific sdcard

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TS-7300 boot sequence

• The TS board now loads the boot sector from the
  SDCard into SDRAM 0x1000
• This code, Thumb mode, is executed and allows
  access to further SDCard sectors and it loads in
  the compressed kernel and initrd into memory
  (the 1st 2 disc partitions)?

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TS-7300 boot sequence
EEPROM
SPI
ARM CPU EEPROM CODE In SRAM
SDCard Boot Sector Partition 1 Partition
2 Partition 3 (rootfs)?
Compressed kernel
SDcard Boot sector
Initrd image
0x1000
0x218000
0x1000000
SDRAM Memory
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TS-7300 boot sequence

• The Compressed kernel code is executed it
  decompresses itself and then loads the initrd
• The initrd loads in the FPGA image and the kernel
  drivers for the SDCard
• The kernel then mounts the 3rd partition on the
  SDCard and pivots root to it. /sbin/init is
  started.
• The system is now up!